A typical data storage system includes one or more data storage disks coaxially mounted on a hub of a spindle motor. The spindle motor rotates the disks at speeds typically on the order of several thousand revolutions-per-minute (RPM). Digital information, representative of various types of data, is typically written to and read from the data storage disks by one or more transducers, or read/write heads, which are mounted to a rotatably mounted actuator and pass over the surface of the rapidly spinning data storage disks.
The actuator typically includes a plurality of outwardly extending actuator arms, with one or more read/write transducer assemblies being mounted resiliently or rigidly on the extreme end of the actuator arms. The actuator arms are interleaved into and out of the stack of rotating disks, typically by means of a coil assembly mounted to the actuator. The coil assembly generally interacts with a permanent magnet structure, and the application of current to the coil assembly in one polarity causes the actuator arms and transducers to shift in one direction, while current of the opposite polarity shifts the actuator arms and transducers in an opposite direction.
In a typical digital data storage system, digital data is stored in the form of magnetic transitions on a series of concentric, closely spaced tracks comprising the surface of the magnetizable rigid data storage disks. The tracks are generally divided into a plurality of sectors, with each sector comprising a number of information fields. One of the information fields is typically designated for storing data, while other fields contain sector identification and synchronization information, for example. Data is transferred to, and retrieved from, specified track and sector locations by the actuator arms and transducers being shifted from track to track, typically under the control of a controller. The transducer assembly typically includes a read element and a write element.
Writing data to a data storage disk generally involves passing a current through the write element of the transducer assembly to produce magnetic lines of flux which magnetize a specific location of the disk surface. Reading data from a specified disk location is typically accomplished by the read element of the transducer assembly sensing the magnetic field or flux lines emanating from the magnetized locations of the disk. As the read element moves over the rotating disk surface, the interaction between the read element and the magnetized locations on the disk surface result in electrical pulses being induced in the read element, thereby indicating transitions in the magnetic field.
It can readily be appreciated that the process of precisely aligning and positioning the transducers over specified disk locations can be adversely affected by vibrations and shocks imparted to, and produced within, the housing of a data storage system. Vibrations from a number of internal and external sources are typically transmitted along the data storage system housing and impinge upon the sensitive system components mounted to the housing. Displacement of a support table or other structure upon which the data storage system is situated, for example, often induces a measurable amount of acceleration in the support structure. A corresponding, but typically amplified, acceleration is transmitted through the housing and the sensitive internal components of the data storage system, such as the spindle motor assembly and the actuator/transducer assembly.
The accelerations imparted to a table or other structure supporting a data storage system typically results in the production of significantly amplified vibrations that are transmitted through the base portion of the housing and other structures coupled to the housing base, such as the spindle motor assembly. The relatively high levels of structural vibration resulting from external housing accelerations and impinging on the spindle motor assembly have been identified as contributing to a number of data storage system maladies, including significant track misalignment errors when reading and writing data to the disks, inaccuracies when reading servo information for locating and aligning the read/write transducers over specified track and sector locations, and an appreciable reduction in the service life of the spindle motor.
Dropping and bumping the data storage system can also dramatically affect the performance and service life of a data storage system. Such mishandling of the data storage system typically results in the production of short duration shock vibrations within the system housing. These short duration shocks are generally associated with appreciable levels of induced housing accelerations which can severally impact the operation and service life of the spindle motor assembly and actuator/transducer assembly. The housing base and other structures that are mechanically coupled to the base typically amplify the detrimental shock vibrations which can cause varying degrees of damage to the data storage system's sensitive components. It is noted that dropping a data storage system on its edge, for example, typically results in the production short duration shock vibrations that impinge on the internal components and structures from a multiplicity of directions.
The vibrations that can adversely affect the performance of the spindle motor and actuator/transducer assembly are generally associated with undesirable levels of acoustic emissions emanating from the housing of the data storage system. The spindle motor, generally rotating at rates on the order of four to five thousand RPM, typically produces mechanically and electrically induced vibrations which are transmitted through the base of the housing and the housing cover. The data storage system housing base, and in particular, the housing cover, greatly amplify the spindle motor excitation vibrations resulting in the production of an appreciable level of undesirable acoustic noise. It is noted that, in general, the operation of the actuator voice coil motor also results in the production and transmission of undesirable vibrations through the data storage system housing, and contributes to the acoustic noise generated by a conventional data storage system.
Various methods and apparatus have been employed in conventional data storage systems in an attempt to dampen external and internal vibrations and accelerations. Such prior art schemes typically employ elastomeric pads or bumpers in an effort to attenuate external vibrations transmitted to the data storage system housing. Elastomeric bosses, for example, have been incorporated as part of the mounting structure between the spindle motor and the base plate to which the spindle motor is mounted, but have generally had limited success due to wear and fatigue of the bosses. Other prior art schemes involve the use of various gaskets and seals employed between the housing base and cover in an attempt to reduce the level of external vibrations imparted on the data storage system housing and to reduce the levels of acoustic noise generated by the system. Such gaskets and sealing methods generally require special installation procedures as any appreciable misalignment or mis-installation of the gasket could compromise the efficacy of the housing seal. Also, the shock isolation methods and apparatus associated with prior art data storage system housings are generally direction sensitive, and thus provide limited attenuation of vibrations emanating from a plurality of sources and directions. Further, conventional shock attenuation apparatus are often bulky, and are generally not suitable for use within the compact housing environment of small and very small form factor data storage systems.